REPLICATED LOCI OF THE
HUMAN pMCH GENES:
ANTISENSE EXPRESSION AND POTENTIAL FOR HOMOLOGOUS RECOMBINATION
Christine L. Miller*,
Margit Burmeiser and Robert C. Thompson
University of Michigan, IL
The pro-melanin concentrating hormone
(pMCH) gene has a feature common to many peptidergic genes, i.e.
the production of a peptide precursor molecule that is then
processed into more than one peptide. However, an additional
layer of complexity exists for the human pMCH gene, located on
chromosome 12q23.1. A 700 bp region of highly homologous sequence
is found in two other sites in the genome, one on 5p14 (pMCHL1)
and the other on 5q13 (pMCHL2). Transcription studies of the
three loci were made possible by radiation-hybrid mapping with
PCR-SSCP and then determining sequence differences between the
two human-variant pro-melanin-concentrating hormone-like genes.
To evaluate the transcription of each locus, we utilized pMCH or
pMCHL-specific primers in RT-PCR of total RNA isolated from human
hypothalamic tissue. The precise identity of the RT-PCR products
was determined by sequencing. A very substantial component of
human pMCH expression was shown to be antisense in orientation.
PMCHL expression was confirmed only for the pMCHL1 locus on 5p14,
and was determined to be unspliced and exclusively antisense in
orientation for a range of RT-PCR primers used. Production of MCH
peptide from the pMCHL loci was effectively ruled out in the
human hypothalamus, whereas production of MCH peptide from the
authentic pMCH locus on 12q would be expected to occur based on
the presence of appropriately spliced sense transcript. It is
possible that the pMCHL1 antisense transcript is involved in
regulation of the pMCH sense RNA. These results are discussed in
the context of the potential for viral-stimulated homologous
recombination between the replicated loci.